Field of the Invention
This invention relates generally to vehicle systems and control processes, such as railway systems including trains travelling in a track or rail network, and in particular to a train control system and method that may be used in connection with electronically-controlled pneumatic (ECP) operations.
Description of Related Art
Vehicle systems and networks exist throughout the world, and, at any point in time, a multitude of vehicles, such as cars, trucks, buses, trains, and the like, are travelling throughout the system and network. With specific reference to trains travelling in a track network, the locomotives of such trains are typically equipped with or operated using train control, communication, and management systems (e.g., positive train control (PTC) systems), such as the I-ETMS® of Wabtec Corp. In order to effectively manage all of the trains, navigation and enforcement systems and processes are implemented, both at the train level and the central dispatch level.
An electronically-controlled pneumatic (ECP)-equipped train relies on electronic signals, rather than changes in brake pipe air pressure, to activate brake valves on individual railcars. The performance and requirements of ECP braking systems are defined by a series of open standards and recommended practices published by the Association of American Railroads (AAR). The primary document is: AAR S-4200: ELECTRONICALLY-CONTROLLED PNEUMATIC (ECP) CABLE-BASED BRAKE SYSTEMS—PERFORMANCE REQUIREMENTS. The AAR S-4200 series of documents is applicable to all ECP system designs in the United States, but has become the recognized standard internationally as well.
With respect to conventional ECP braking systems, when an external penalty input is active (e.g., during a cab signal or other penalty condition), the head end unit (HEU) typically transmits a Train Brake Command (TBC) of 100% (i.e., a full service brake command) on the trainline to the ECP devices in the individual railcars to instruct the individual railcars to apply brakes. The TBC is communicated as a percentage, for example, a “0% TBC” indicates that ECP brakes are being commanded to release, while a “100% TBC” signifies that ECP brakes are being commanded to deliver a full (i.e., maximum) brake application. A penalty brake application of ECP brakes (i.e., an ECP brake application typically initiated by an external safety system to override a train operator's control) is always a “100% TBC” command from the HEU. However, in conventional ECP operations, a single point failure involving the HEU, for example, a software or hardware failure of the HEU, can prevent the TBC from being successfully transmitted to the railcars. For example, it is possible that the other ECP devices on the railcars may receive a TBC of “0%” when the ECP system is requesting a penalty brake TBC of “100%”. This failure is a significant safety risk, because it allows ECP brakes to remain released in a situation where an external safety system is attempting to apply the ECP brakes. If a fault prevents the TBC from being successfully transmitted, it is left to the operator to manually apply a pneumatic emergency brake application.
For at least these reasons, there is a need in the art for improved systems and methods for ECP operations.